The present invention relates to an improved pluggable electronic module configured to connect and/or convert data signals from a first serial transmission medium to a second serial transmission medium. A preferred embodiment of the invention relates particularly to an improved GigaBaud Interface Converter (GBIC) as defined by the GBIC specification, the teaching of which is hereby incorporated herein by reference. However, the improvements disclosed in this specification are applicable to high speed data communication modules other than GBICs as well.
The GBIC specification was developed by a group of electronics manufacturers in order to arrive at a standard small form factor transceiver module for use with a wide variety of serial transmission media and connectors. The specification defines the electronic, electrical, and physical interface of a removable serial transceiver module designed to operate at Gigabaud speeds. A GBIC provides a small form factor pluggable module which may be inserted and removed from a host or switch chassis without powering off the receiving socket. The GBIC standard allows a single standard interface to be changed from a first serial medium to an alternate serial medium by simply removing a first GBIC module and plugging in a second GBIC having the desired alternate media interface.
The GBIC form factor defines a module housing which includes a first electrical connector for connecting the module to a host device or chassis. This first electrical connector mates with a standard socket which provides the interface between the host device printed circuit board and the module. Every GBIC has an identical first connector such that any GBIC will be accepted by any mating GBIC socket. The opposite end of the GBIC module includes a media connector which can be configured to support any high performance serial technology. These high performance technologies include: 100 Mbyte multi-mode short wave laser without OFC; 100 Mbyte single-mode long-wave laser with 10 km range; Style 1 intracabinet differential ECL; and Style 2 intracabinet differential ECL.
The GBIC module itself is designed to slide into a mounting slot formed within the chassis of a host device. The mounting slot may include guide rails extending back from the opening in the chassis wall. At the rear of the mounting slot the first electrical connector engages the mating socket which is mounted to a printed circuit board within the host device. The GBIC specification requires two guide tabs to be integrated with the electrical connector. As the connector is mated with the socket, the guide tabs of the connector engage similar structures integrally formed with the socket. The guide tabs are to be connected to circuit ground on both the host and the GBIC. The guide tabs engage before any of the contact pins within the connector and provide for static discharge prior to supplying voltage to the module. When the GBIC is fully inserted in this manner, and the connector fully mated with the socket then only the media connector extends beyond the host device chassis.
Copper GBIC's allow the host devices to communicate over a typical copper serial transmission medium. Typically this will comprise a shielded cable comprising two or four twisted pairs of conductors. In such GBIC's, the media connector will generally be a standard DB-9 electrical connector, or an HSSDC connector at each end. In the case of copper GBIC's this DB-9 or HSSDC connector is a purely passive device and serves no other function than to connect electrical signals between the cable and the GBIC module. Thus, it may be desirable to eliminate the media connector altogether, and directly attach two copper GBIC's, one at each end of the copper cable, thereby eliminating two connectors and reducing the cost of the data link. It may be further desired to make such direct attach copper GBIC's field installable such that the transmission cable may be routed and installed prior to attaching the GBIC modules. Such field installable GBIC's would help reduce the risk of damage to the modules while the wiring is being installed.
In designing GBIC modules, a factor which must be considered is that GBICs are high frequency devices designed to operate at speeds above 1 Gigabit per second. Thus, the modules carry the potential of emitting high frequency signals to the surrounding area which may adversely affect sensitive equipment situated nearby. Therefore, a sophisticated shielding mechanism is required in order to prevent such unwanted emissions. In prior art modules, this has generally included a metallized or metal clad portion of the module located adjacent the media connector. The metal portion is configured to engage the chassis wall of the host device when the module is fully inserted into the mounting slot. The metallized portion of the module and the chassis wall form a continuous metal barrier surrounding the mounting slot opening. The metal barrier blocks any high frequency emissions from escaping from the host chassis due to a gap between the GBIC module and the chassis mounting slot. A disadvantage of prior art GBIC modules, however, is that spurious emissions are free to escape the module directly through the media connector. This leakage has the potential of disrupting the operation of nearby devices. The problem is most acute in so called "copper GBICs" where an electrical connector is provided as the media connector. Furthermore, most prior art GBIC modules are formed of a plastic outer housing which allows EMI signals generated by the GBIC to propagate, freely within the chassis of the host device. These emissions can interfere with other components mounted within the host chassis and can further add to the leakage problem at the media end of the GBIC module.
Therefore, what is needed is an improved high speed pluggable communication module having an improved media connector end which acts to block all spurious emissions from escaping beyond the module housing. Such an improved module should be adaptable to function as a Giga-Bit interface converter module and interface with any GBIC receptacle socket. In such a module, the host connector should conform to the GBIC specification, and include the requisite guide tabs connected to the circuit ground. At the media end of the module, the improved module may include either an DB-9 style 1 copper connector, an HSSDC style 2 copper connector, or an SC duplex fiber optic connector as the second end media connector. Alternately, the module may provide for the direct attachment of the module to a copper transmission medium such that a single shielded copper cable may be interconnected between two host devices with an individual GBIC connected at each end. It is further desired that the module include plastic latching tabs to affirmatively lock the module into a corresponding host socket. Internally, the module should contain whatever electronics are necessary to properly convert the data signals from the copper transmission medium of the host device to whichever medium is to be connected to the media end of the module. In the case of GBIC modules, all of the operating parameters as well as mechanical and electrical requirements of the GBIC specification should be met by the improved module. However, though it is most desired to provide an improved GBIC module, it must be noted that the novel aspects of a transceiver module solving the problems outlined above may be practiced with high speed serial modules other than GBICS.